1. Field of the Invention
The present invention relates to an electrical leak detecting apparatus for an electric vehicle, and more particularly, to an electrical leak detecting apparatus for an electric vehicle, which is capable of not only detecting an electrical leak generated when a vehicle body is connected to the maximum potential or minimum potential of a battery pack, but also detecting which portion of the battery pack the vehicle body is connected to when an electrical leak is generated through the connection of the vehicle body and an intermediate potential of the battery pack.
2. Description of the Related Art
Electric vehicles use a high voltage of about 1000 V as a driving source. Thus, a battery pack that is a driving source of an electric vehicle is separated from a vehicle body and should be maintained in an insulating state from the vehicle body.
However, when an electrical leak is generated when the vehicle body is connected to the battery pack of the electric vehicle due to an accident, an unknown cause or the like, a human life as well as the damage of the electric vehicle may be lost due to a high voltage of the battery pack.
Thus, the electric vehicle includes an essential element, such as an electrical leak detecting apparatus for detecting an electrical leak generated when the vehicle body is connected to the battery pack.
FIG. 1 is a conventional electrical leak detecting apparatus for an electric vehicle 120.
The conventional electrical leak detecting apparatus for the electric vehicle 120 illustrated in FIG. 1 is connected between a battery pack 110 and a vehicle body GND and detects an electrical leak generated when the vehicle body GND is connected to the battery pack 110. The conventional electrical leak detecting apparatus for the electric vehicle 120 illustrated in FIG. 1 equalizes a resistor between the electric pack 110 and the vehicle body GND and expresses the equalized resistor as an insulation resistor Rf. When the battery pack 110 and the vehicle body GND are normally maintained in an insulating state, the resistance value of the insulation resistor Rf is infinity, and current is cut off and does not flow through the conventional electrical leak detecting apparatus for the electric vehicle 120. However, when an abnormality occurs in the battery pack 110 and an electrical leak is generated in the vehicle body GND, the resistance value of the insulation resistor Rf is decreased. Thus, a closed circuit is formed between the battery pack 110, the insulation resistor Rf, the conventional electrical leak detecting apparatus for the electric vehicle 120, and the vehicle body GND, respectively, so that current flows through the conventional electrical leak detecting apparatus for the electric vehicle 120. The conventional electrical leak detecting apparatus for the electric vehicle 120 detects an electrical leak between the battery pack 110 and the vehicle body GND by using this principle. In FIG. 1, L is a load that uses a power of the battery pack 110.
The conventional electrical leak detecting apparatus for the electric vehicle 120 includes a voltage distribution resistor Rs, a detection resistor Rm, and a measured potential supply unit Vdc, which are connected to one another in series between a minimum potential terminal of the battery pack 110 and the vehicle body GND. The conventional electrical leak detecting apparatus for the electric vehicle 120 further includes first and second polarity conversion switches SW3 and SW4 between the detection resistor Rm and the measured potential supply unit Vdc. In this regard, the first and second polarity conversion switches SW3 and SW4 are connected to each other and convert the polarity of the measured potential supply unit Vdc connected between the battery pack 110 and the vehicle body GND. In other words, when the first and second polarity conversion switches SW3 and SW4 are connected to an a-point, a positive electrode of the measured potential supply unit Vdc is connected to the detection resistor Rm. Also, a negative electrode of the measured potential supply unit Vdc is connected to the vehicle body GND, and the battery pack 110 and the measured potential supply unit Vdc are connected to each other in a forward direction. When the first and second polarity conversion switches SW3 and SW4 are connected to a b-point, the negative electrode of the measured potential supply unit Vdc is connected to the detection resistor Rm. Also, the positive electrode of the measured potential supply unit Vdc is connected to the vehicle body GND, and the battery pack 110 and the measured potential supply unit Vdc are connected in a backward direction.
The operation of the conventional electrical leak detecting apparatus for the electric vehicle 120 will now be described with reference to FIG. 2.
Hereinafter, the conventional electrical leak detecting apparatus for the electric vehicle 120 when an electrical leak is generated when the vehicle body GND is connected to the maximum potential terminal of the battery pack 110 will be described. The conventional electrical leak detecting apparatus for the electric vehicle 120 equalizes a resistor between the maximum potential terminal of the battery pack 110 and the vehicle body GND and expresses the equalized resistor as a maximum potential insulation resistor Rf1. When an electrical leak is generated when the vehicle body GND is connected to the maximum potential terminal of the battery pack 110, current flows through the conventional electrical leak detecting apparatus for the electric vehicle 120 via the maximum potential insulation resistor Rf1. In this regard, when the first and second polarity conversion switches SW3 and SW4 are connected to the a-point as illustrated in FIG. 2, a closed circuit is formed between the battery pack 110, the maximum potential insulation resistor Rf1, the measured potential supply unit Vdc connected to the battery pack 110 in the forward direction, the detection resistor Rm, and the voltage distribution resistor Rs, respectively, so that current flows through the conventional electrical leak detecting apparatus for the electric vehicle 120, as illustrated in FIG. 3. The conventional electrical leak detecting apparatus for the electric vehicle 120 measures a both terminal voltage Vm of the detection resistor Rm to calculate a value of the maximum potential insulation resistor Rf1, thereby detecting an electrical leak of the electric vehicle.
In this regard, the both terminal voltage Vm of the detection resistor Rm measured by the conventional electrical leak detecting apparatus for the electric vehicle 120 may be expressed using Equation 1. Here, a voltage of the battery pack 110 is expressed in Equation 1 and the following Equations as (V1+V2) for better understanding, and the voltage of the battery pack 110 is not limited to (V1+V2):
                              V                      m            +                          =                                            R              m                                                      R                s                            +                              R                m                            +                              Rf                1                                              ⁢                                    (                                                V                  1                                +                                  V                  2                                +                                  V                  dc                                            )                        .                                              Equation        ⁢                                  ⁢        1            
As shown in Equation 1, the value of the maximum potential insulation resistor Rf1 may be obtained by obtaining (V1+V2) that is the voltage of the battery pack 110. If the expression of the both terminal voltage Vm is obtained using only the measured potential supply unit Vdc without being affected by (V1+V2) that is the voltage of the battery pack 110, the following operation should be further performed.
In detail, the first and second polarity conversion switches SW3 and SW4 of the conventional electrical leak detecting apparatus for the electric vehicle 120 are respectively connected to the b-point, as illustrated in FIG. 4. Then, a closed circuit is formed between the battery pack 110, the maximum potential insulation resistor Rf1, the measured potential supply unit Vdc connected to the battery pack 110 in the backward direction, the detection resistor Rm, and the voltage distribution resistor Rs, respectively, so that current flows through the conventional electrical leak detecting apparatus for the electric vehicle 120, as illustrated in FIG. 5. In this regard, the voltage Vm as shown in Equation 2 is detected from the detection resistor Rm:
                              V                      m            -                          =                                            R              m                                                      R                s                            +                              R                m                            +                              Rf                1                                              ⁢                                    (                                                V                  1                                +                                  V                  2                                +                                  V                                      d                    ⁢                                                                                  ⁢                    c                                                              )                        .                                              Equation        ⁢                                  ⁢        2            
As known from Equations 1 and 2, when an electrical leak is generated when the vehicle body GND is connected to the maximum potential terminal of the battery pack 110, the voltage Vm applied to both terminals of the detection resistor Rm is the sum (V1+V2) of voltages of the battery pack 110 and is comparatively high voltage. Thus, the conventional electrical leak detecting apparatus for the electric vehicle 120 may measure the both terminal voltage Vm easily and precisely.
When Equation 2 is subtracted from Equation 1 and the result of subtraction is divided by 2, the voltage Vm applied to the detection resistor Rm is expressed using Equation 3:
      V    m    =                    R        m                              R          s                +                  R          m                +                  Rf          1                      ⁢                  (                  V                      d            ⁢                                                  ⁢            c                          )            .      
The value of the maximum potential insulation resistor Rf1 equalized by Equation 3 may be obtained using Equation 4. Thus, the conventional electrical leak detecting apparatus for the electric vehicle 120 may determine an electrical leak by using the resistance value of the equalized maximum potential insulation resistor Rf1:
                              Rf          1                =                                                            R                m                                            V                m                                      ⁢                          (                              V                                  d                  ⁢                                                                          ⁢                  c                                            )                                -                                    (                                                R                  s                                +                                  R                  m                                            )                        .                                              Equation        ⁢                                  ⁢        4            
Hereinafter, the conventional electrical leak detecting apparatus for the electric vehicle 120 when an electrical leak is generated when the vehicle body GND is connected to the minimum potential terminal of the battery pack 10 will be described. The conventional electrical leak detecting apparatus for the electric vehicle 120 equalizes a resistor between the minimum potential terminal of the battery pack 110 and the vehicle body GND and expresses the equalized resistor as a minimum potential insulation resistor Rf2. When an electrical leak is generated when the vehicle body GND is connected to the minimum potential terminal of the battery pack 110, current flows through the conventional electrical leak detecting apparatus for the electric vehicle 120 via the equalized minimum potential insulation resistor Rf2. In this regard, when the first and second polarity conversion switches SW3 and SW4 are connected to the a-point as illustrated in FIG. 6, a closed circuit is formed between the voltage distribution resistor Rs, the detection resistor Rm, the measured potential supply unit Vdc connected to the detection resistor Rm in a forward direction, and the minimum potential insulation resistor Rf2, respectively, so that current flows through the conventional electrical leak detecting apparatus for the electric vehicle 120, as illustrated in FIG. 7. The conventional electrical leak detecting apparatus for the electric vehicle 120 measures the both terminal voltage Vm of the detection resistor Rm to calculate a value of the minimum potential insulation resistor Rf2, thereby detecting an electrical leak of the electric vehicle. In this regard, the both terminal voltage Vm of the detection resistor Rm measured by the conventional electrical leak detecting apparatus for the electric vehicle 120 may be expressed using Equation 5:
                              V                      m            +                          =                                            R              m                                                      R                s                            +                              R                m                            +                              Rf                2                                              ⁢                                    (                              +                                  V                                      d                    ⁢                                                                                  ⁢                    c                                                              )                        .                                              Equation        ⁢                                  ⁢        5            
Obviously, when the first and second polarity conversion switches SW3 and SW4 are respectively connected to the b-point as illustrated in FIG. 8, a closed circuit is formed between the voltage distribution resistor Rs, the detection resistor Rm, the measured potential supply unit Vdc connected to the detection resistor Rm in a backward direction, and the minimum potential insulation resistor Rf2, respectively, so that current flows through the conventional electrical leak detecting apparatus for the electric vehicle 120. In this regard, the both terminal voltage Vm as shown in Equation 6 is measured from the detection resistor Rm:
                              V                      m            -                          =                                            R              m                                                      R                s                            +                              R                m                            +                              Rf                2                                              ⁢                                    (                              -                                  V                                      d                    ⁢                                                                                  ⁢                    c                                                              )                        .                                              Equation        ⁢                                  ⁢        6            
The both terminal voltage Vm measured by the conventional electrical leak detecting apparatus for the electric vehicle 120 may be expressed using Equation 7 by subtracting Equation 6 from Equation 5 and by dividing the result of subtraction by 2. The value of the minimum potential insulation resistor Rf2 equalized by Equation 7 may be calculated using Equation 8. The conventional electrical leak detecting apparatus for the electric vehicle 120 may determine an electrical leak by using the value of the equalized minimum potential insulation resistor Rf2:
                                          V            m                    =                                                    R                m                                                              R                  s                                +                                  R                  m                                +                                  Rf                  2                                                      ⁢                          (                              V                                                                                          ⁢                                      d                    ⁢                                                                                  ⁢                    c                                                              )                                      ,                            Equation        ⁢                                  ⁢        7                                          Rf          2                =                                                            R                m                                            V                m                                      ⁢                          (                              V                                  d                  ⁢                                                                          ⁢                  c                                            )                                -                                    (                                                R                  s                                +                                  R                  m                                            )                        .                                              Equation        ⁢                                  ⁢        8            
In this regard, as known from Equations 5 and 6, when an electrical leak is generated when the vehicle body GND is connected to the minimum potential terminal of the battery pack 110, the voltage Vm applied to both terminals of the detection resistor Rm is obtained only from the measured potential supply unit Vdc. The measured potential supply unit Vdc is much smaller than the voltage of the battery pack 110. Thus, it is very difficult to precisely measure the both terminal voltage Vm of the detection resistor Rm by using the conventional electrical leak detecting apparatus for the electric vehicle 120 due to low detection sensitivity. Thus, it is very difficult to determine an electrical leak.
Also, the conventional electrical leak detecting apparatus for the electric vehicle 120 detects an electrical leak by using the same method and the same Equation regardless of an electrical leak generated when the vehicle body GND is connected to the maximum potential terminal of the battery pack 110, an electrical leak generated when the vehicle body GND is connected to the minimum potential terminal of the battery pack 110, or an electrical leak generated when the vehicle body GND is connected to an intermediate potential of the battery pack 110. Then, the conventional electrical leak detecting apparatus for the electric vehicle 120 may determine an electrical leak of the battery pack 110 but may not precisely detect a place where an electrical leak is generated.